A Donor–Acceptor Cage for Thermally Activated Delayed Fluorescence: toward a New Kind of TADF Exciplex Emitters

We present the rational design of an organic cage combining an electron-donating (D) triazatruxene and electron-accepting (A) triphenyl triazine connected by three electronically inert pillars. This controlled architecture leads to a precise spatial separation and cofacial alignment of the D and A motifs. Such an architecture induces an efficient intramolecular through-space charge transfer (TSCT), providing a small singlet–triplet energy difference (ΔEST) of 0.049 eV, and thus gives rise to a thermally activated delayed fluorescence (TADF) macrocyclic exciplex emitter.